"This is the first example outside of primates of a species being able to do this," says Scarf.

While the mathematical abilities of humans are undoubtedly unique, there is some evidence that other animals understand numbers and order.

Nearly 15 years ago, researchers found macaque monkeys were able to order images based on the number of objects shown in them.

Now, after carrying out the same test on three pigeons, Scarf and colleagues have found these small-brained animals also have this ability.

"I don't think people have a very glowing view of the pigeon's intelligence," says Scarf.

"[But] you don't need a primate brain to be able to do things like this."

Scarf and colleagues first trained the birds in boxes fitted with computer touch screens. The pigeons were shown a series of three images, each with one, two or three different objects in it.

The birds were trained, using a food reward, to pick the images in ascending order of the number of objects in them (by pecking the screen).

To control for the possibility that the pigeons were responding to a visual cue other than the number of objects, Scarf and colleagues used images that had a mix of shape, sizes, colours and total surface area.

"That was to force the pigeons to use number rather than other stimuli," says Scarf.

The researchers then tested the pigeons' ability to order pairs of completely new numbers between 1 and 9 and found the birds ordered the pairs correctly 74 per cent of the time.

Pigeons slower than monkeys

But while pigeons showed the same ability as monkeys, they did take longer to train - a year, compared to a couple of months for monkeys, says Scarf.

"You have to give them lots and lots of examples before they get that numbers are the critical variable ... whereas monkeys are much better at picking up on things like that," he says.

In addition, says Scarf, some birds have a better personality for learning than others.

"Some pigeons are really quick to finish their tasks and other pigeons are bit more casual," he says.

The new findings also raise questions about the origins of such numerical abilities.

"Birds separated from mammals about 300 million years ago so either we're looking at an ability that came from a common ancestor or we're looking at something that's evolved independently in the two lines," says Scarf.

He says it is important to see how widespread such numerical abilities are in the animal kingdom.

"It would be amazing to look at an animal that is not a mammal and not a bird - an octopus or something else really 'out there'," says Scarf.

He says future research could also study whether pigeons can carry out basic addition and subtraction, something that monkeys have also been shown to be capable of.